This invention relates to methods and machines for screeding, i.e., spreading, distributing, smoothing and/or leveling, placed and/or poured, uncured concrete, sand, gravel or like loose, spreadable materials, and, more particularly, to an apparatus and method for screeding such materials with a vehicle either positioned adjacent the uncured concrete or driven through the uncured concrete while screeding the material behind the vehicle without the use of prepositioned guides or rails.
In the concrete placement industry, it is necessary to "strike-off", smooth and level, i.e., "screed" areas of placed and/or poured concrete before curing. Numerous methods and techniques for spreading and leveling the concrete have been used in the past. These include passing an edge of a two by four plank across the top of the concrete as well as more sophisticated, power screeds. For instance, in the construction of bridges or highways, or even large concrete floor areas such as in warehouses, large rail or guide supported screeds are often used. Such screeds include long trusses or beams which span the width of the strip of concrete to be formed and ride on heavy guides or rails adjacent either side of the concrete strip to skim or smooth the top of the concrete between the rails.
In highway construction, slip-form pavers are often used. Such pavers include self-propelled vehicles having hoppers and pouring apparatus for laying a strip of concrete followed by a screed which spreads and smooths the concrete immediately after it is placed and/or poured by the machine. Such machines run on wheels or tracks and follow guide lines or strings such that the concrete strip is laid in the desired path.
Often, smaller concrete laying jobs under 50,000 square feet or those which require low slump concrete do not justify the expense of setting up heavy guides or rails and the movement of large machinery to ride on such rails. Similarly, slip-form pavers are too large to justify use on such small jobs. Moreover, many previously known screeding machines have been unable to lay more than a single strip of concrete in a day since it is necessary that one edge of a previous strip be used as a form, guide or support to lay the next strip. Thus, until the previous concrete strip has hardened, additional strips cannot be laid side by side.
Coupled with the above is the requirement on smaller concrete jobs of forming and/or hand finishing the edges of the concrete areas. If such finish work together with the primary screeding of the main areas is done by hand, the task is highly labor intensive, very time consuming and expensive.
Accordingly, the present invention was devised in recognition of the problems of finishing both large and small placed and/or poured concrete areas, especially those which do not justify the time and expense of moving and setting up heavy, rail guided paving or screeding machines or slip-form pavers. It was also desired to provide an apparatus and method which would significantly reduce the labor involved in laying and finishing large, nonstrip-type concrete areas in a manner which would allow completion in a continuous work session without laying the concrete in side by side strips on successive days. Further, it was desired to provide an apparatus and method which would allow operation for concrete or other loose material finishing by a single operator while providing screeded concrete or smooth, leveled material with close height tolerances in a manner which would allow reduction of labor expense.